Comparative Proteomic Analysis by Isobaric Tags for the Relative and Absolute Quantification Reveals the Responses of Tobacco (Nicotiana tabacum L.) Roots to Different Soil Types

Integratedly analyzed quantitative proteomics with transcriptomics to discover key genes via fg-1 non-heading mutant in the early heading stage of Chinese cabbage

Leaf heading is an important agronomic trait of Chinese cabbage, which directly affects its yield. Leaf heading formation in Chinese cabbage is controlled by its internal genotype and external environmental factors, the underlying mechanism of which remains poorly understood. To discover the leaf heading formation mechanism more deeply, this study analyzed the correlation between proteomic and transcriptomic data in the leaf heading formation mutant fg-1 generated by EMS. iTRAQ-based quantitative proteomics techniques were performed to identify the protein expression profiles during the key periods of the early heading stage in the section of the soft leaf apical region (section a) and the whole leaf basal region (section d). We first identified 1,246 differentially expressed proteins (DEPs) in section a and 1,055 DEPs in section d. Notably, transcriptome-proteome integrated analysis revealed that 207 and 278 genes showed consistent trends at the genes' and proteins' expression levels in section a and section d, respectively. KEGG analyses showed that the phenylpropanoid biosynthesis pathway was enriched in both sections a and d. Furthermore, 86 TFs exhibited co-upregulation or co-downregulation, and seven out of 86 were involved in plant hormone synthesis and signal transduction pathways. This indicates that they are potentially related to the leaf heading formation in Chinese cabbage. Taken together, we have identified several key early-heading-formation-related factors via integration analysis of the transcriptomics and proteomics data. This provides sufficient gene resources to discover the molecular mechanism of leaf heading formation.

Effects of mulch films with different thicknesses on the microbial community of tobacco rhizosphere soil in Yunnan laterite

The mulch film (MF) management model of the agricultural field affects the physical and chemical properties of soil (PCPS) and the structure of the microorganism community; however, studies on the relationship between the rhizosphere microorganism community structure and the thickness of MF are still limited. To understand the interactions among the MF thickness, PCPS, and rhizosphere microorganism, a study was conducted by using an integrated metagenomic strategy, where tobacco rhizosphere soil was treated with four commonly representative and used thicknesses of MFs (0.004, 0.006, 0.008, and 0.010 mm) in Yunnan laterite. The results showed that agronomic traits such as the tobacco plant height (TPH), leaf number (LN), fresh leaf weight (FLW), and dry leaf weight (DLW) were significantly (p < 0.01) improved in the field mulched with the thickest film (0.010 mm) compared with the exposed field (CK), and there was a 6.81 and 5.54% increase in the FLW and TPH, separately. The correlation analyses revealed a significant positive correlation of the MF thickness with the soil water content (SWC), soil organic matter (SOM), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), and available phosphorus (AP; all p < 0.01), while the MF thickness was negatively correlated with the soil temperature (ST; p < 0.01). In addition, the community structure of the rhizosphere soil bacteria was significantly changed overall by the MF thickness, which also interfered with the function of the rhizosphere soil bacteria. The correlation analyses also showed that the abundance of Bradyrhizobium and Nitrospira was positively correlated with the MF thickness, while the abundance of Sphinsinomonas and Massilia was negatively correlated with it. This indicated that with the increase of the MF thickness, the ability of the rhizosphere soil to utilize N and remove harmful molecules was strengthened, while the capacity of the rhizosphere soil to degrade pollutants was greatly reduced. These findings provide additional insights into the potential risks of the application of different thicknesses of MFs, particularly concerning the PCPS and soil microbial communities.

Effects of Exocellobiohydrolase CBHA on Fermentation of Tobacco Leaves

The quality of tobacco is directly affected by macromolecular content, fermentation is an effective method to improve biochemical properties. In this study, we utilized CBHA (cellobiohydrolase A) glycosylase, which was expressed by Pichia pastoris, as an additive for fermentation. The contents of main chemical components of tobacco leaves after fermentation were determined, and the changes of microbial community structure and abundance in tobacco leaves during fermentation were analyzed. The relationship between chemical composition and changes in microbial composition was investigated, and the function of bacteria and fungi in fermentation was predicted to identify possible metabolic pathways. After 48 h of CBHA fermentation, the contents of starch, cellulose and total nitrogen in tobacco leaf decreased by 17.60%, 28.91% and 16.05%, respectively. The microbial community structure changed significantly, with Aspergillus abundance decreasing significantly, while Filobasidum, Cladosporium, Bullera, Komagataella, etc., increased in CBHA treated group. Soluble sugar was most affected by microbial community in tobacco leaves, which was negatively correlated with starch, cellulose and total nitrogen. During the fermentation process, the relative abundance of metabolism-related functional genes increased, and the expressions of cellulase and endopeptidase also increased. The results showed that the changes of bacterial community and dominant microbial community on tobacco leaves affected the content of chemical components in tobacco leaves, and adding CBHA for fermentation had a positive effect on improving the quality of tobacco leaves.

The Effects of Increasing the Dry-Bulb Temperature during the Stem-Drying Stage on the Quality of Upper Leaves of Flue-Cured Tobacco

The control of the curing temperature during the stem-drying stage is important for the quality of upper leaves of flue-cured tobacco. Based on the conventional curing process during the yellowing stage and the leaf0drying stage in the tobacco curing process, in this study, the dry-bulb temperature was increased to 72 and 75 °C in the bulk curing barn during the stem-drying stage to compare with the highest temperature of 68 °C commonly adopted in the bulk curing barn. The result showed that, compared with the conventional temperature setting, the energy consumption cost was reduced by 0.10 or 0.08 USD/kg when the curing temperature was increased to 72 or 75 °C, respectively. Statistical analysis showed that increasing DBT was beneficial to the improvement in the internal quality of flue-cured tobacco leaves. The adjustment of curing temperature also improved the aromatic quality and volume of singe-material tobacco leaves. However, as the temperature continued to increase, the quality improvement in cured upper tobacco leaves showed a decreasing trend. According to the quality of fresh tobacco leaves, an appropriate increase in the dry-bulb temperature based on the conventional temperature setting of 68 °C during the stem-drying stage can improve the usability and economic benefit. The degree of increase in the DBT should depend on the quality of local fresh tobacco growth in the field.